Amphoteric optical brighteners, their aqueous solutions, their production and their use

ABSTRACT

Water soluble, amphoteric optical brighteners (W) comprising at least one brightener-characteristic radical X which contain at least one anionic substituent and covalently linked over at least one tertiary amino group Z to at least one non-chromophoric, essentially aliphatic, polyquaternary ammonium-hydrocarbon radical Y containing more than one quaternary ammonium group and in which each hydrocarbon radical is optionally interrupted by and/or substituted with one or more further heteroatoms, have surprising brightening properties, especially in papermaking, and in the form of their aqueous solutions are of notable stability.

In the production of paper it is usual to employ retention agents,dewatering agents and/or fixatives in order to improve the speed ofproduction or other properties and yield of the product. These adjuvantsare mostly of cationic character, and if it is desired to produce anoptically brightened paper, care should be taken that with the use of ananionic optical brightener there does not occur a precipitation byinteraction of the anionic and cationic substances. In order to avoidsuch an undesirable precipitation, the cationic agents are usually addedat a sufficient time after the addition of the anionic component, eitherwithin a very short time range immediately before sheet formation (i.e.a few seconds before conveying the pulp to the paper sheet forming partof the assembly) or after sheet formation.

In GB-A-1489595 there is described a broad range of optical brightenersof the 4,4′-bis-(triazinylamino)-stilbene-2,2′-disulphonic acid series,containing at the triazinyl ring a defined substituent which is an aminogroup that contains a second nitrogen which is of amidic or basiccharacter. If this second nitrogen is of basic character the opticalbrightener is amphoteric. Such amphoteric optical brighteners arehowever difficult to synthesize and, as the ionic character of theiraqueous solutions varies with the pH, their stability may varyaccordingly; the Examples of this GB-A-1489595 are all directed tooptical brighteners in which said second nitrogen is of amidiccharacter. The optical brighteners in GB-A-1489595 are described asbeing generically applicable to substrates of cellulose, wool, syntheticpolyamide or polyurethane, including among others also paper, but theyare particularly intended for the optical brightening of textile fibersand detergents.

In papermaking there are still usually employed anionic opticalbrighteners, mainly of the4,4′-bis-(triazinylamino)-stilbene-2,2′-disulphonic acid series, onetypical representative being an optical brightener of the formula

which is in particular employed in the size press.

It has now surprisingly been found that certain amphoteric products withoptical brightening properties, as defined below, especially in aqueoussolution, more particularly in concentrated aqueous solution, arevaluable multi-functional agents that combine the activity of opticalbrighteners and of cationic adjuvants—especially if they are ofpolymeric character—(e.g. as retention assistants, drainage assistantsor fixative in paper production), which in the production of opticallybrightened paper allows the addition of optical brightener at any timebefore, during or after sheet formation. Further they are also ofunexpected compatibility with anionic adjuvants used in papermaking.Furthermore it has also surprisingly been found that aqueous solutionsof these amphoteric optical brighteners are of unexpected stability.

The invention relates to the defined amphoteric optical brighteners andtheir aqueous solutions, and to their production and use.

The invention thus provides a water soluble, amphoteric opticalbrightener (W) comprising at least one brightener-characteristic radicalX of an anionic optical brightener of the4,4′-bistriazinylaminostilbene-2,2′-disulphonic acid series whichcontains the group of formula

and is covalently linked over at least one tertiary amino group Z to atleast one non-chromophoric, essentially aliphatic, poly(quaternaryammonium)-hydrocarbon radical Y containing more than one quaternaryammonium group and in which each hydrocarbon radical is optionallyinterrupted by and/or substituted with one or more further heteroatoms.

These amphoteric optical brighteners may thus also be represented asessentially consisting of constituent units of the average formulaX′-Z-Y′  (I_(W)),in which

-   -   X′ signifies one equivalent of X, i.e. X divided by its covalent        valence,        and    -   Y′ signifies one equivalent of Y, i.e. Y divided by its covalent        valence.

As brightener-characteristic radical X there is meant the essentialstructural component of conventional optical brighteners of the4,4′-bistriazinylaminostilbene-2,2′-disulphonic acid series, containingthe characteristic conjugation system which provides the typicalUV-light absorption and fluorescence properties of the opticalbrightener.

Further the optical brightener radical X contains anionic substituent,in particular as otherwise conventionally present in anionic opticalbrighteners of the 4,4′-bistriazinylaminostilbene-2,2′-disulphonic acidseries, mainly sulphonic acid groups and optionally carboxylic acidgroups, which preferably are in salt form. The optical brightenerradical may be the radical of any anionic optical brightener of the4,4′-bistriazinylaminostilbene-2,2′-disulphonic acid series, whichcontains the characteristic group of formula (x).

The poly(quaternary ammonium)-hydrocarbon radicals Y preferably containfurther heteroatoms, more preferably oxygen in the form of ether bridgesand/or hydroxy groups. The poly(quaternary ammonium)-hydrocarbonradicals Y may optionally be crosslinked to higher polymeric forms.

The water soluble, amphoteric optical brighteners (W) of the inventionmay be produced by means of addition and condensation reactions of akind conventional per se, in particular by reacting underdehydrohalogenating conditions an optical brightener precursor thatcontains at least one reactive halogen, with a suitable, correspondingsecondary amine that contains more than one quaternary ammonium groupand/or with a corresponding non-quaternary precursor thereof and thenquaternizing the reaction product. More particularly the process for theproduction of the amphoteric optical brighteners of the invention ischaracterised in that an optical brightener precursor (B) of formulaX-(Hal)_(m)  (I),wherein

-   -   Hal signifies halogen, preferably chlorine,        and    -   m signifies an integer in the range of 1 to 4,        is reacted under dehydrohalogenating conditions with an amine        (P_(A)) of formula        (HNZ″)_(n)-Y″  (II),        wherein    -   Y″ has the significance of Y or signifies a non-quaternary        precursor of Y,    -   Z″ has the significance of Z if Y″ has the significance of Y or,        if Y″ is a non-quaternary precursor of Y, is a group of formula        —NR₀— in which R₀ is a low molecular aliphatic radical which is        optionally substituted with hydroxy, nitrile or carbamoyl and is        optionally interrupted by oxygen, or is a bond to Y″,        and    -   n signifies the number of reactive tertiary amino groups linked        to Y″ and is at least 1,        and, if Y″ is a non-quaternary precursor of Y, it is further        reacted with a reactant (Q) suitable for introducing at least        one quaternary ammonium group and/or quaternizing at least one        quaternizable amino group.

As optical brightener precursor especially of formula (I) there may beemployed any conventional intermediate as typically employed forproducing corresponding anionic optical brighteners of thebistriazinylaminostilbene disulphonic acid series, e.g. of the formula

wherein

-   -   R₁, R₂, R₃ and R₄ signify, independently from each other, the        radical of an amine or of an alcohol,        and    -   M signifies hydrogen, low molecular ammonium or an alkali metal        cation,

In the significances of R₁, R₂, R₃ and R₄ the radical of an alcohol isusually the radical of an aliphatic alcohol or of a phenol. The radicalof the aliphatic alcohol is mostly C₁₋₄-alkoxy, the phenol radical ismostly unsubstituted phenoxy. The amine radical is e.g. optionallysubstituted anilino or an aliphatic aminogroup —NR₀′R₀″,

wherein

-   -   R₀′ signifies hydrogen, C₁₋₄-alkyl, benzyl, C₂₋₃-hydroxyalkyl or        carboxy-(C₁₋₄-alkyl),    -   R₀″ signifies hydrogen, C₁₋₄-alkyl, C₂₋₃-hydroxyalkyl,        sulpho-C₁₋₃-alkyl, sulpho-C₃₋₄-hydroxyalkyl, cyano-(C₁₋₃-alkyl),        carbamoyl-(C₁₋₃-alkyl), carboxy-(C₁₋₄-alkyl),        carboxy-[cyano-(C₂₋₃-alkyl)], carboxy-[carbamoyl-(C₂₋₃-alkyl)]        or dicarboxy-(C₂₋₃-alkyl),        or    -   R₀′ and R₀″ together with the nitrogen to which they are linked        form a heterocycle,        R₁ and R₃ preferably signify an optionally substituted anilino        group of formula        wherein    -   R₀′″ signifies hydrogen, methyl, methoxy or chlorine, preferably        hydrogen,        and    -   p signifies 0, 1 or 2,        or an aliphatic aminogroup —NR₀′R₀″,

R₀′ preferably signifies C₁₋₂-alkyl, benzyl, C₂₋₃-hydroxyalkyl orcarboxy-(C₁₋₂-alkyl).

R₀″ preferably signifies C₂₋₃-hydroxyalkyl, carbamoyl-(C₁₋₃-alkyl),cyano-(C₁₋₃-alkyl) or carboxy-(C₁₋₂-alkyl).

If R₀′ and R₀″ together with the nitrogen to which they are linked forma heterocycle, this is preferably a morpholine ring or acarboxypyrrolidine ring,

R₂ and R₄ preferably signify methoxy, phenoxy or more preferably analiphatic aminogroup —NR₀′R₀″,

The two symbols R₁ and R₃ in formula (I) may have the same significanceor different significances. Preferably they have the same significance.

Similarly also the two symbols R₂ and R₄ in formula (I) may have thesame significance or different significances. Preferably they have thesame significance.

The corresponding precursors within the scope of formula (I) may berepresented by the formula

wherein

-   -   R₁₀, R₂₀, R₃₀ and R₄₀, independently from each other, signify        chlorine or have one of the significances of R₁, R₂, R₃ or R₄        respectively,        with the proviso that at least one of R₁₀, R₂₀, R₃₀ and R₄₀        signifies chlorine.

Preferred optical brightener precursors of formula (Ib) are those inwhich two of R₁₀, R₂₀, R₃₀ and R₄₀, more preferably R₂₀ and R₄₀ signifychlorine, especially those in which R₁₀ and R₃₀ signify each a radicalof formula (a). Particularly preferred precursors of formula (Ib) maythus be represented by the following formula

The reactant for introducing the polyquaternary ammonium-hydrocarbonradicals Y (linked over Z) is in particular a secondary amine thatpreferably already contains a corresponding number of quaternaryammonium groups, and preferably contains further heteroatoms, preferablyoxygen atoms Preferably this reactant, which above is represented bymeans of formula (II), is an oligocondensate of a chloroterminatedadduct of epichlorohydrin to an aliphatic oligohydroxy compound with twospecies of amines (A), the one being amines (A₁), i.e.

-   -   (A₁′) a monoamine suitable for introducing a quaternary ammonium        group        or    -   (A₁″) a diamine or higher functional optionally further        substituted polyamine in which the aminogroups are tertiary        aminogroups and which does not contain any primary or secondary        amino groups, suitable for introducing one or more quaternary        ammonium groups        or a combination of both,        and the other being    -   (A₂) a mono-primary amine which on reaction with the chlorine of        the adduct gives a secondary aminogroup,        so that this product is capable of reacting by means of the        secondary aminogroup with a halogen of the optical brightener        precursor (B).

The epichlorohydrin-derived condensates are preferably polyquaternary,and may be crosslinked polymers obtainable by an at least three-stagesynthesis, in which in the first stage epichlorohydrin is reacted with ahydroxy compound to give a chloroterminated adduct; in the second stagethe chloroterminated adduct is reacted with an amine suitable forintroducing a quaternary ammonium group, in particular—for theproduction of crosslinked products—a secondary amine or an at leastbifunctional tertiary amine, leaving some terminal chlorine unreactedfor further reaction with the primary amine (A₂); and in the third stage(A₂) is reacted with this chlorine.

As starting hydroxy compounds there may be employed preferably fullyaliphatic compounds, e.g. mono- or oligo-functional alcohols.

Suitable hydroxy compounds are bi- to hexa-functional aliphatic alcoholswith up to six, preferably three to six, carbon atoms in the hydrocarbonradical, in particular of the following formulaR—(OH)_(x1)  (III),in which

-   -   R signifies the x1-valent radical of a C₃₋₆-alkane        and    -   x1 signifies a number from 3 to the number of carbon atoms in X,        or a mixture of oligohydroxyalkanes of formula (III),        or a mixture one or more oligohydroxyalkanes of formula (III),        with a C₂₋₃-alkanediol,        or polyalkyleneglycols, in particular of the average formula        HO-(Alkylene-O)_(x2)—H  (IV),        wherein    -   Alkylene signifies C₂₋₄-alkylene        and    -   x2 signifies a number from 2 to 40.

Preferred compounds of formula (Va) are those of formulaH—(CHOH)_(x3)—H  (III′)with x3 being 3 to 6.

Alkylene in formula (IV) is ethylene, propylene and/or butylene and thepolyalkyleneglycols of formula (IV) may be homo- or copolymers,preferably water soluble products (with a solubility in water of atleast 10 g/l at 20° C. and pH 7). As polyalkyleneglycols of formula (IV)there are preferably employed polyethyleneglycols orcopolyalkyleneglycols containing a prevailing molar proportion ofethyleneoxy-units. More preferably there are employedpolyethyleneglycols, i.e. compounds of formula (IV) in which Alkylenesignifies only ethylene.

By the reaction of the hydroxy groups with the epichlorohydrin the epoxyring of the epichlorohydrin is opened and a corresponding adduct isformed which contains a 2-hydroxy-3-chloropropyl-1 radical. Thisreaction is preferably carried out in the absence of any other solventand, especially for hydroxy, in the presence of a catalyst, which ise.g. a Lewis acid, preferably boron trifluoride e.g. in the form of itsetherate or acetic acid complex. This reaction is exothermic and theepichlorohydrin reacts with the available hydroxy groups and, asreaction proceeds, may also react with a hydroxy group of a2-hydroxy-3-chloropropyl-1 radical formed during the reaction, so thatsome of the hydroxy groups in a polyfunctional starting reactant [e.g.of formula (III)] may even remain non-reacted. Depending on the molarratio, on the functionality of the starting hydroxycompound and on itsconfiguration—especially if x1 in formula (III) is 4 to 6—the degree ofreaction of the x1 OH groups with epichlorohydrin may vary, and may e.g.be in the range of 15 to 95%, mostly 30 to 90%, of the total number ofOH groups originally present in the starting polyol. The obtained adductis a chloro-terminated product.

The chloroterminated adduct is then reacted with a suitable amine toproduce a polyquaternary optionally crosslinked product, e.g. with asimple tertiary amine or with a crosslinking reactant that is capable ofproviding a bridging quaternary ammonium group, which suitably is atertiary oligoamine or a secondary monoamine. Such amines preferablycorrespond to the following formula

in which

-   -   Y signifies C₂₋₃-alkylene,    -   y signifies a number from 0 to 3,    -   R′ signifies C₁₋₃-alkyl or C₂₋₃-hydroxyalkyl        and    -   R″ has a significance of R′, if y is 1 to 3,        -   or signifies hydrogen, if y is 0,            especially as a reactant leading to a crosslinking, where            the starting oligohydroxycompound is of formula (III),            or to the formula            N(R′)₃  (VI),            wherein    -   each symbol R′ has the above indicated significance, or the        three symbols R′ together with the nitrogen to which they are        linked, form a pyridine or methylpyridine ring,        or        wherein    -   R′″ signifies C₁₋₃-alkyl        and    -   w signifies a number from 2 to 6,        the amines of formulae (VI) and (VII) being especially suitable        as reactants, where the starting oligohydroxycompound is of        formula (IV).

For an optional chain-terminating, quaternizing reaction there may e.g.be employed a tertiary monoamine preferably of formula (VI).

As amino compounds of formula (V) there may be employed known amines.The C₁₋₃-alkyl radicals in R′ and R″ may be methyl, ethyl, propyl orisopropyl, the lower molecular ones being preferred, especially methyl.The C₂₋₃-hydroxyalkyl radicals are preferably 2-hydroxyethyl or -propyl.Among the C₁₋₃-alkyl radicals and the C₂₋₃-hydroxyalkyl radicals theC₁₋₃-alkyl radicals are preferred, especially methyl. The index y may beany number from 0 to 3 preferably 0 to 2, more preferably 0 or 1.Representative amines of formula (V) are dimethylamine, diethanolamine,tetramethylethylenediamine, tetramethylpropylenediamine,N,N-diethanol-N′,N′-dimethylethylenedamine,pentamethyldiethylenetriamine and hexamethyltriethylenetetramine, amongwhich the difunctional amines, in particular the lower molecular ones,are preferred, especially dimethylamine and tetramethylethylenediamine.Representative amines of formula (VI) are trimethylamine, triethylamine,dimethylethanolamine, methyldiethanolamine, triethanolamine andpyridine, among which trimethylamine and triethylamine are preferred. Informula (VII) the index w preferably is 2 or 3. Representative amines offormula (VII) are tetramethylethylenediamine,tetramethylpropylenediamine andN,N-diethanol-N′,N′-dimethylethylenediamine.

Suitable monoprimary amines (A₂) are for instance mono-C₁₋₄-alkyl-aminesoptionally substituted with hydroxy, methoxy, tertiary amino, —CN or—CONH₂, e.g. mono-C₂₋₄-hydroxyalkyl-amines, mono-methyl-amine,mono-ethyl-amine, mono-isopropyl-amine, mono-ethanol-amine,mono-isopropanol-amine, N,N-dimethylaminopropylamine andN,N-diethanolaminopropylamine.

The polycationic polyquaternary products may be polymers at leastinsofar as the reaction with the amine may lead to a polymer or thestarting product is polymeric (e.g. is a polyalkylene glycol) or both.

The molar ratio of quaternizing amine to epichlorohydrin adduct issuitably chosen so that a polyquaternary intermediate product isproduced which has at least one unreacted chlorine available in themolecule for reaction with the primary amine.

Suitable monoprimary amines (A₂) correspond e.g. to the followingformulaH₂N-Alkylene-G  (VIII),wherein

-   -   Alkylene signifies C₂₋₄-alkylene        and    -   G signifies hydrogen, C₁₋₂-alkoxy, CN, CONH₂ or —N(R′)₂.

The molar ratio of quaternizing amine to epichlorohydrin adduct of acompound of formula (III) may e.g. be chosen so that for everymole-equivalent of adduct (with reference to chlorine) there is employed0.1 to 0.3 moles of amine ±30%, e.g. ±10%, if the reaction is acrosslinking or up to twice this quantity if the reaction is not acrosslinking. The molar ratio of quaternizing amine to epichlorohydrinadduct of a compound of formula (IV) may e.g. be chosen so that forevery mole-equivalent of adduct (with reference to chlorine) there isemployed 0.6 mole of amine of formula (VII) ±30%, e.g. ±10%, if thereaction is a crosslinking or up to twice this quantity if the reactionis not a crosslinking. The molar ratio of quaternizing amine toepichlorohydrin adduct of a compound of formula (IV) may e.g. be chosenso that for every mole-equivalent of adduct (with reference to chlorine)there is employed 0.4 mole of amine of formula (VI) ±40%, e.g. ±20%.Depending on the chosen reaction components and conditions and on theenvisaged product, a preferred or optimum ratio may be chosen by meansof a few preliminary tests.

The non-reacted chlorines of the product are reacted with the primaryamine, preferably to at least 70%, more preferably exhaustively.

The concentration of the reactants is preferably chosen in such a waythat the concentration of (P_(A)) in the aqueous mixture is in the rangeof 10 to 75%, preferably 20 to 70% by weight.

The reaction of quaternizing amine with the adduct is carried outpreferably in aqueous medium and preferably with heating, e.g. at atemperature in the range of 50 to 100° C., preferably 60 to 90° C.During the reaction, at least at the beginning, the basicity of theamine is sufficient for the quaternizing alkylation of the amine withthe adduct, i.e. with the chloride used as an alkylating agent. The pHof the reaction mixture is preferably in the range of 4 to 9, at thebeginning being preferably in the range of 7 to 9. As reaction proceeds,the alkalinity of the mixture and the concentration of crosslinkingamine diminish. If in the reaction product there is present a proportionof covalently linked chlorine which is higher than desired, there maye.g. be added a further reactant which is a monofunctional tertiaryamine and/or, if the starting crosslinking reactant is a secondarymonoamine, there may be added a suitable strong base, such as an alkalimetal hydroxide, preferably sodium hydroxide, so that the pH ispreferably maintained in the range of 7 to 9. When the reaction with thefirst species of amines, i.e. quaternising, has completed or has reachedthe desired degree, the second species, i.e. the primary amine, is addedand reaction is continued. If desired, when also this reaction hascompleted, the reaction mixture may be acidified by addition of aconventional acid, preferably a mineral acid (such as hydrochloric acid,sulphuric acid or phosphoric acid) or a low molecular aliphaticcarboxylic acid e.g. with 1 to 6 carbon atoms (such as formic acid,acetic acid, citric acid or lactic acid), e.g. to reach a pH below 7,more preferably in the range of 4 to 7, most preferably in the range of5 to 6.5. Usually such an acidification is however not necessary. Ifquaternization is carried out with crosslinking, the progress of thecrosslinking reaction may be followed by checking the viscosity of thereaction mixture, which gives an empirical impression of the degree ofcrosslinking. A suitable viscosity is e.g. in the range of 200 to 3000cP. According to a preferred feature of the process, the quaternizationis carried out without crosslinking.

The reaction with the primary amine is carried out preferably withstirring and heating, for instance at a temperature in the range of 50to 120° C., preferably 60 to 100° C. The reaction is advantageouslycarried out with the aid of a dehydrochlorinating adjuvant, inparticular a base, preferably alkali metal hydroxide carbonate orbicarbonate.

The reaction of (P_(A)) with the optical brightener precursor (B) may becarried out at temperatures and pH ranges as usually suitable forreacting the respective halogens, in particular chlorine atoms, of theabove precursors, for instance at temperatures in the range of 20 to100° C. and at pH values in the range of 4 to 10, depending on thenumber of chlorine atoms in particular; for instance if in formula (Ib)all four of R₁₀, R₂₀, R₃₀ and R₄₀ signify chlorine, two of them may bereacted under acidic to neutral conditions (e.g. pH 4 to 7) and attemperatures in the range of 20 to 50° C., while the two furtherchlorine atoms may then be reacted under stronger reaction conditions,e.g. at pH values in the range of 6 to 10 and at temperatures in therange are 40 to 100° C. Where (B) contains two or more reactive halogenatoms, the resulting product (W) may, if desired, also becorrespondingly chain-extended or/and (further) crosslinked.

The obtained aqueous composition of (W), i.e. (W_(A)), is an aqueoussolution, i.e. a true or at least colloidal solution, in whichpreferably the sulpho groups are in salt form, more preferably non-innersalt form; the pH of (W_(A)) is preferably basic, e.g. up to pH 10,advantageously in the range of pH 7.5 to 9.5. The viscosity of thesolution of (W) may e.g. be in the same range as above, i.e. in therange of 200 to 3000 cP. (W_(A)) may be used directly as produced, inparticular in the concentrated form as produced, or—if desired—it may bemodified in salt content and/or concentration e.g. by membranefiltration, and/or it may be combined with any further desiredcomponents, in particular with an additive that protects the compositionagainst any harmful influence of microorganisms, e.g. with an additivethat stops the growth of disturbing microorganisms or with a biocide,e.g. as commercially available, and in a concentration as usuallyreccommended for such additives, e.g. in a concentration of 0.001 to0.1% by weight referred to the liquid composition. The (W)-content ofthe concentrated aqueous solutions (W_(A)) may range in a broad scopeand it is possible to prepare highly concentrated solutions, e.g. of a(W)-concentration of up to 80% by weight, e.g. in the range of 20 to 80%by weight, preferably 30 to 80% by weight.

The so produced compositions combine the properties of component (B) asan optical brightener and of the cationic component (P_(A)), which maye.g. be an internal or external functional additive in papermaking, forinstance a flocculant, drainage assistant, retention adjuvant or afixative, or may just otherwise modify the optical brightener, andprovide an amphoteric product of surprising properties and compatibilityat any stage of paper production and also in sizes and coatings. The (W)composition (W_(A)) of the invention provides in particular thepossibility of adding the anionic optical brightener at any time before,during or after formation of the paper web or sheet. This means that themulti-functional composition of the invention may be added also in theaqueous stock, without it being necessary to immediately make the papersheet.

The amphoteric products (W) of the invention are also compatible withother cationic additives or components that might be present or added inthe stock, e.g. retention aids and/or cationic surfactants.

A particular feature of the invention is thus represented also by theprocess for the production of optically brightened paper wherein anaqueous (W)-solution as defined above is employed as a functionalinternal or external additive, optionally in the presence of othercationic additives.

The amphoteric products (W) of the invention, expediently in the form ofan aqueous composition (W_(A)) as produced by the method describedabove, may thus serve simultaneously as assistants in the production ofpaper, in particular as fixatives, for reducing the amount of backwatercomponents, e.g. turbidity, in backwaters (white waters) from paperproduction, and as optical brighteners for producing opticallybrightened paper.

The invention thus provides also a method for producing paper, inpartticular a paper web or sheet, from aqueous stock, wherein (W) isemployed as an adjuvant, especially as a fixative. As “paper” there isintended herein also paper board and cast paper shapes. As an aqueousstock there is intended any stock, in particular cellulosic stock, asemployed for papermaking and wherein the pulp suspension may derive fromany origin as conventionally employed for papermaking, e.g. virgin fiber(chemical or mechanical pulp), machine broke (in particular coatedbroke) and reclaimed paper (especially deinked and optionally bleachedreclaimed paper). The aqueous paper pulp or stock may also containfurther additions as may be desired for a certain quality, such assizing agents, fillers, flocculating agents, drainage and/or retentionassistants, which are preferably added after the addition of (W). Thestock concentration may vary in any conventional range as suitable forthe employed pulp, machine, process and desired paper quality, e.g. inthe range of 0.4 to 10%, preferably 0.8 to 6%, by weight of dry pulp.According to a particular feature of the invention there is employed apulp from coated broke and/or bleached, deinked reclaimed paperoptionally blended with other pulp.

The amphoteric polycationic products (W) are preferably employed in aconcentration in the range of 0.05 to 0.5% by weight, more preferably0.1 to 0.4% by weight referred to dry pulp. The pH may be in the weaklybasic to distinctly acidic range, preferably in the range of pH 4 to pH8, more preferably pH 5 to pH 7. The paper may be produced using anyconventional paper making machines and in a manner conventional per se.The resulting backwater is of reduced contaminants content, inparticular of reduced turbidity, and consequently the respective BODand/or COD values are also reduced. By the use of (W) there may also beachieved an improvement of the efficiency of other cationic wet-endadditives such as flocculants, retention assistants or drainageassistants, and there may be obtained paper of optimum quality while theoccurrence of paper breakings due to disturbing anionic contaminants iscorrespondingly reduced, while the efficiency of the optical brighteneris optimal and there is obtainable paper of very regular whiteness inhigh yield. The so produced paper may in particular be employed as asubstrate for ink-jet-printing.

The amphoteric optical brighteners of the invention may be applied inany stage and composition for papermaking, in particular also in aqueoussize compositions and in coating pastes, and thus the invention providesalso an aqueous paper size composition comprising an amphoteric opticalbrightener (W) of the invention and conventional further paper sizecomponents, and furthermore the invention provides also an aqueous papercoating paste comprising an amphoteric optical brightener (W) of theinvention and conventional further coating paste components, especiallyfillers and/or pigments and optionally a resin and/or binder andoptionally a surfactant, where these conventional components may inparticular be employed in concentrations as otherwise usually employedin size or coating compositions.

It has further surprisingly been found that by cationically modifyingthe inorganic pigments or fillers with the amphoteric products (W) orrespectively their aqueous composition (W_(A)) products as definedabove, there may be achieved products of notable properties e.g. in thebrightness of the inorganic products, or in the physical form of thetreated inorganic substances, such as workability and regulardistribution in suspension.

The invention thus also provides a cationically modified white pigment(W_(P)) in particulate form, essentially consisting of a particulateinorganic white pigment (M) of a particle size in the range of 0.1 to 40μm and an applied amphoteric product (W).

The invention thus more particularly concerns the stated modification ofparticulate inorganic white pigments (M) by (W) to the cationicallymodified products (W_(P)).

(M) comprise in general known inorganic substances as usually employedas white pigments or fillers (or loading agents), and which moreparticularly are conventionally employed in non-coloured form especiallyin papermaking, and as may also be employed in other fields of techniquesuch as paints, lacquers, cosmetics, plastics, construction materialetc. Mainly concerned are those for papermaking, since in papermakingindustry problems exist with the quenching of optical brightening agentsby additives used to improve retention and drainage during thepapermaking process.

The term “pigment” as used herein is intended to comprise also the term“filler”, insofar as a same substance may be used as filler or pigment.

The inorganic pigment (M) may be any such substance, naturally occurringand optionally physically modified, or synthetically produced, andpreferably as employed in particular in paper coatings or as fillers orloading agents in the paper sheet, as added e.g. in the size or also inthe paper pulp suspension. (M) may include mineral substances andsynthetically produced inorganic substances, such as silica, alumina,titanium dioxide, zinc oxide and sulphide, and inorganic salts, e.g.silicates, aluminates, titanates, sulphates and carbonates, of lowvalence metal ions, mainly of alkali metal ions, alkaline earth metalions or earth metal ions, especially of sodium, potassium, magnesium,calcium, barium and/or aluminium. The following may be mentioned asexamples: titanium dioxides (rutile, anatase), potassium titanates, zincoxide, zinc sulphide, lithopone, calcium sulphates (gypsum oranhydrite), various forms of silica (e.g. amorphous silica such asdiatomite), alumina trihydrate, sodium silico-aluminate, talc(MgO.4SiO₂.H₂O), barium sulphate (baryte, blanc fixe), calciumsulphoaluminate (satin white), chrysotile, china clay in various degreesof whiteness (mainly comprising Al₂O₃.SiO₂.H₂O and optionally furthermetal oxides such as iron oxide, titanium dioxide, magnesium oxide,calcium oxide, sodium oxide and/or potassium oxide) and calciumcarbonate in various forms (mineral natural form or syntheticprecipitated and/or crystallised forms). They may be employed in theforms as commercially available, in particular of various degrees ofwhiteness, e.g. of a whiteness >80, mostly >82 (measured according toISO methods), but also less white products may be used, e.g. of awhiteness ≦82, or even ≦80, e.g. in the range of 70 to 80.

The particle size of (M) is on average in the range of 0.1 to 40 μm, asobtainable by conventional methods, e.g. by grinding and/or millingand/or—if required—sieving and screening, or by suitable precipitationand/or (micro)crystallisation methods. Commercially available productsmostly contain in general a certain proportion of particles smaller than0.1 μm (dust) and/or some granules larger than 40 μm; preferably theselarger size components are ≦20% by weight, more preferably ≦10% byweight. Preferably the average particle size of such inorganic pigments(M) is within the range of 0.1 to 20 μm, more preferably 0.2 to 10 μm,most preferably 0.2 to 5 μm, preferably at least 75%, preferably ≧80% ofthe particles being within these ranges. Among the mentioned pigments(M) are preferred those comprising silicates, in particular kaolin, andespecially those comprising carbonates, in particular calciumcarbonates.

The inorganic pigment (M) may comprise a conventional dispersant orwetting agent as commercially available, on its surface, e.g.polyphosphates, in a suitable low concentration as usual e.g. <0.5% byweight, preferably <0.3% by weight. For the purpose of the invention thepresence of such a surfactant is not essential and (M) may also beexempt of a dispersant or wetting agent.

As mentioned above, (M) may be employed in the forms as commerciallyavailable, in particular it may be employed in dry form or in the formof a concentrated aqueous slurry, e.g. with a solids content in therange of 40 to 70% by weight.

Preferred pigments and fillers (M) have e.g. a specific surface area inthe range of 5 to 24 m²/g, preferably 7 to 18 m²/g.

For the production of the cationically modified pigment (W_(P)) (M) maythus be mixed with (W_(A)).

According to a further variant a solution of (W_(A)), may be sprayed ona dry (M)-powder with mixing.

The produced aqueous (W_(P))-suspension may, if desired, be filtered anddried to a white pigment (W_(P)) in dry, particulate form ofcorresponding particle size. If desired it may be agglomerated to largeragglomerate particles, e.g. by compaction e.g. to granules, pellets ortablets.

The invention thus also provides a process for the production of a whitepigment (W_(P)) in the form of an aqueous suspension, wherein an aqueoussupension of (M) is admixed with (W_(A)) and also a process for theproduction of a white pigment (W_(P)) in dry form, wherein an aqueoussupension of (M) is admixed with (W_(A)), the suspension is filtered andthe residue is dried and optionally compacted.

This process is in particular carried out substantially in the absenceof further functional additives that would interfere in a disturbing waywith the reaction, in particular in the absence of other functionalpapermaking additives and components (such as resins, fibres and/orpaper-size components).

The weight ratio of (W) to (M) may range broadly, depending on thedesired degree of cationic modification of (M) in (W_(P)); it may e.g.range in the scope of 0.01:100 to 10:100, preferably 0.2:100 to 5:100,more preferably 0.3:100 to 4:100. For compacted dry forms this weightratio is preferably in the range of 0.01:100 to 3:100, more preferably0.2:100 to 2:100.

(W) may be applied in the form of an aqueous solution—e.g. of aconcentration in the range 0.1 g/l to the saturation limit—to (M) by anysuitable method. If (M) is used in the form of an aqueous slurry,(W_(A)) is preferably a concentrated solution—e.g. of a concentration inthe range 1 g/l to the saturation limit, preferably in the range of 5g/l to 40 g/l—and may be mixed with it in the desired proportion e.g. byplain stirring and optionally with heating or cooling, e.g. at atemperature in the range of 5 to 60° C., preferably 10 to 40° C., morepreferably with slight heating e.g. in the temperature range of 25 to40° C. or at ambient conditions without any heating or cooling. If (M)is in the dry form, a sprayable, preferably more diluted solution of(W)—e.g. of a concentration in the range of 0.1 to 20 g/l, preferably0.5 to 10 g/l—may e.g. be applied by spraying and mixing, optionallywith heating or cooling, e.g. at a temperature in the range of 5 to 60°C., preferably 10 to 40° C., more preferably with slight heating e.g. inthe temperature range of 25 to 40° C. or at ambient conditions withoutany heating or cooling.

The pH of the solution (W_(A)) may range broadly, e.g. from the weaklyacidic to weakly basic range, in particular from pH 5 to pH 8,preferably pH 5.5 to pH 7.5.

According to the invention there may be produced amphoteric opticalbrightener solutions, namely (W_(A)), of high stability and of notableperformance properties, in particular in the production of opticallybrightened paper and in the treatment of inorganic white pigments orfillers, especially in degree of whiteness and yield.

In the following Examples parts and percentages are by weight, if nototherwise indicated; parts by weight relate to parts by volume as gramsto milliliters; the temperatures are indicated in degrees Celsius; inApplication Examples C and D °SR signifies degrees Schopper-Riegler andthe percentages relate to the weight of the starting aqueous pulpsuspension.

EXAMPLE 1 Amphoteric Optical Brightener 1

A mixture of 35.2 parts D-sorbitol and 17.8 parts glycerol is heated to90° C. until a solution forms. The stirred solution is cooled to 80° C.,and treated with 0.25 parts boron trifluoride-acetic acid complex.Stirring is continued at 80° C. for 10 minutes until the catalyst isfully dispersed. To the stirred mixture is then added 136.4 parts ofepichlorohydrin over 1 hour at 80–85° C. Once addition is complete, thereaction mixture is cooled to 30° C., treated with 99.8 partsN,N-dimethylethanolamine and heated at 90° C. for 3 hours. The reactionmixture is then further treated with 17.1 parts ethanolamine at 90° C.for 2 hours to give a water-miscible, cationic intermediate (1c).

The intermediate (1c) is stirred at 50–60° C. and treated with 100.7parts of the optical brightener precursor of formula (1a),

in the form of a 20% aqueous suspension, and 18.1 parts sodiumbicarbonate. The reaction mixture is heated to reflux for 4 hours togive an aqueous solution of the amphoteric optical brightener 1, whichcan be used as is.

EXAMPLE 2 Amphoteric Optical Brightener 2

A mixture of 35.2 parts D-sorbitol and 17.8 parts glycerol is heated to90° C. until a solution forms. The stirred solution is cooled to 80° C.,and treated with 0.25 parts boron trifluoride-acetic acid complex.Stirring is continued at 80° C. for 10 minutes until the catalyst isfully dispersed. To the stirred mixture is then added 64.2 parts ofepichlorohydrin over 1 hour at 80–85° C. Once addition is complete, thereaction mixture is cooled to 30° C., treated with 50.0 partstriethylamine and heated at 90° C. for 3 hours. The reaction mixture isthen further treated with 12.4 parts isopropanolamine at 90° C. for 2hours to give a water-miscible, cationic intermediate (2c).

The intermediate (2c) is stirred at 50–60° C. and treated with 86.2parts of the optical brightener precursor of formula (2a)

in the form of a 30% aqueous suspension, and 12.9 parts sodiumbicarbonate. The reaction mixture is heated to reflux for 4 hours togive an aqueous solution of the amphoteric optical brightener 2 whichcan be used as is.

EXAMPLE 3 Amphoteric Optical Brightener 3

A mixture of 35.2 parts D-sorbitol and 17.8 parts glycerol is heated to90° C. until a solution forms. The stirred solution is cooled to 80° C.,and treated with 0.25 parts boron trifluoride-acetic acid complex.Stirring is continued at 80° C. for 10 minutes until the catalyst isfully dispersed. To the stirred mixture is then added 106.0 parts ofepichlorohydrin over 1 hour at 80–85° C. Once addition is complete, thereaction mixture is cooled to 30° C., treated with 19.4 partsdimethylamine, in the form of a 60% aqueous solution, and heated to 90°C. for 1 hour. The reaction mixture is cooled to 55° C., and the pHadjusted to 8 using a 30% aqueous solution of sodium hydroxide. After 1hour at 55–60° C., the reaction mixture is treated with 17.5 partsethanolamine and heated at 95–100° C. and pH 8 (30% sodium hydroxide)for a further 2 hours to give a water-miscible, cationic intermediate(3c).

The intermediate (3c) is stirred at 50–60° C. and treated with 102.8parts of optical brightener precursor (1a), in the form of a 20% aqueoussuspension. The reaction mixture is heated to 95–100° C. for 4 hours atpH 8 (30% sodium hydroxide) to give an aqueous solution of theamphoteric brightener 3 which can be used as is.

EXAMPLE 4 Amphoteric Optical Brightener 4

A mixture of 35.2 parts D-sorbitol and 17.8 parts glycerol is heated to90° C. until a solution forms. The stirred solution is cooled to 80° C.,and treated with 0.25 parts boron trifluoride-acetic acid complex.Stirring is continued at 80° C. for 10 minutes until the catalyst isfully dispersed. To the stirred mixture is then added 106.0 parts ofepichlorohydrin over 1 hour at 80–85° C. Once addition is complete, thereaction mixture is cooled to 30° C., treated with 56.5 partsN,N-dimethylethanolamine and heated at 90° C. for 2 hours. The reactionmixture is then sequentially treated with 21.0 partsN,N,N′,N′-tetramethylethylene diamine for 2 hours at 90° C. and with 5.6parts ethanolamine for 2 hours at 90° C. to give a water-miscible,cationic intermediate (4c).

The intermediate is stirred at 50–60° C. and treated with 39.4 partsoptical brightener precursor of formula (2a), in the form of a 30%aqueous suspension, and 5.9 parts sodium bicarbonate. The reactionmixture is heated to reflux for 4 hours to give an aqueous solution ofthe amphoteric brightener 4 which can be used as is.

Application Example A

Sizing solutions are prepared by adding a pre-determined amount of thebrightener solution to a stirred aqueous solution of a cationic starch(Chargemaster™ R467 from Grain Processing Corporation, Iowa) and a 40%aqueous solution of low molecular mass poly(diallyidimethylammoniumchloride) at 60° C. The solution is diluted with water to a starchconcentration of 5% and a poly(diallyidimethylammonium chloride)concentration of 2.5%, then allowed to cool.

The sizing solution is poured between the moving rollers of a laboratorysize-press and applied to a commercial 75 g/m² neutral-sized white paperbase sheet. The treated paper is dried for 5 minutes at 70° C. in a flatbed drier. The dried paper is allowed to condition, then measured forCIE Whiteness on a calibrated Elrepho spectrophotometer.

A comparison between amphoteric optical brightener 1 and opticalbrightener 5 of formula

representative of the state-of-the-art, demonstrates the improvedperformance of the compound of the invention in a strongly cationicsize.

CIE whiteness Amphoteric Optical Concentration in mmol/kg Brightener 1Optical Brightener 5 0 81.8 81.8 1.25 93.1 94.1 2.5 96 93.4 5.0 100.5 897.5 100.8 87.8

Analogously as the optical brightener 1, each of the optical brighteners2, 3 and 4 can be used in Application Example A.

Application Example B

Sizing solutions are prepared by adding a pre-determined amount of thebrightener solution to a stirred aqueous solution of an anionic oxidisedpotato starch (Perfectamyl™ A4692) at 60° C. The solution is dilutedwith water to a starch concentration of 5%, then allowed to cool.

Brightened papers were then prepared as descibed in Application ExampleA.

A comparison between the amphoteric optical brightener 2 and opticalbrightener 5, representative of the state-of-the-art, demonstrates theimproved performance of the compound of the invention in an anionicsize.

CIE whiteness Amphoteric Optical Concentration in mmol/kg Brightener 2Optical Brightener 5 0 81.7 81.7 1.25 94.5 92.1 2.5 101.4 99.3 5.0 109105.9 7.5 112.8 109.8 10.0 115.5 112.8

Analogously as the optical brightener 2, each of the optical brighteners1, 3 and 4 can be used in Application Example A.

Production Examples of White Pigments (WP)

10 parts of a filler or pigment (M_(X)) are mixed in a suitable vesselwith 300 parts of water and x parts of cationic product (W) in the formof aqueous concentrate produced in the above Examples are added theretowith the aid of further 80 parts of water and the mixture is stirredduring 5 minutes at 400 rpm and then suction-filtered through a glassfibre paper filter. The moist filter pad is transferred to a drying ovenand dried at 30° C. The dried product is then ground to a fine powder ofaverage particle size of 1 μm with >80%<2 μm and <2%>10 μm.

x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 and 0.8.

If desired, before filtering, the product may be treated with an opticalbrightener.

The dried powder may directly be employed. For measuring the whitenessit may shaped into tablets by means of a tablet press. The tablet may beused for measuring the whiteness, e.g. by means of a spectrophotometer(Minolta CM-3700d).

The following cationically modified pigments (WP_(X)) are produced withthe following fillers or pigments (M_(X)):

-   for (WP_(X1))-   (M_(X1)) Fine, white, high purity calcium carbonate with a density    by ISO 787/10 of 2.7, commercially available under the trade name    HYDROCARB OG of Plüss-Stauffer AG, Oftringen, Switzerland-   for (WP_(X2))-   (M_(X2)) Very fine, white, natural microcrystalline calcium    carbonate (calcite) slurry with a density of 1.89, commercially    available under the trade name HYDROCARB 90M slurry from Omya UK or    resp. Croxton and Garry Limited.-   for (WP_(X3))-   (M_(X3)) calcium carbonate commercially available under the trade    name SNOWCAL 60 from Omya UK or resp. Croxton and Garry Limited.-   for (WP_(X4))-   (M_(X4)) Precipitated calcium carbonate commercially available under    the trade name HAKUENKA TDD from Omya UK.-   for (WP_(X5))-   (M_(X5)) Fine, white, highly refined clay commercially available    under the trade name SUPREME from EEC International Ltd.-   for (WP_(X6))-   (M_(X6)) Fine, white, highly refined clay commercially available    under the trade name SPESWHITE from EEC International Ltd.-   for (WP_(X7))-   (M_(X7)) Fine, white, high purity coating clay commercially    available under the trade name SPS from EEC International Ltd.-   for (WP_(X8))-   (M_(X8)) China Clay grade B from EEC International Ltd.

Application Example C

A coating composition is prepared containing 3000 parts of thecationically modified chalk (W_(X1)) treated with the product of Example1, 18 parts cationic dispersing agent, and 600 parts latex (a copolymerof n-butyl acrylate and styrene latex of pH 7.5–8.5, commerciallyavailable under the trade name ACRONAL S320D). The solids content isadjusted to 55% by the addition of water. The so prepared coatingcomposition is then applied to a commercial 75 g/m² neutral-sized (withconventional alkyl ketene dimer), bleached paper base sheet, using anautomatic wire-wound bar applicator with a standard speed setting and astandard load on the bar. The coated paper is dried for 5 minutes at 70°C. in a hot air flow. The dried paper is allowed to condition, thenmeasured for CIE whiteness on a calibrated Datacolor ELREPHO 2000spectrophotometer. The measured values show a surprisingly highwhiteness degree and yield.

Application Example D

200 g of a pulp suspension (2.5% aqueous suspension of a 50% mixture ofbleached soft wood and hard wood pulps beaten to a freeness of about20°SR) is measured into a beaker and stirred, then 40% filler suspension[80 g of 100 g/liter (W_(X3)) in water] is added. After the addition themixture is stirred for a further 0.5 minutes and then 1.7% (3.4 g) ofneutral size is added (typically a dispersion of 2.5 g of Aquapel 360Xin water—Aquapel 360X is an alkylketene dimer size suspension fromHercules Ltd.). After the addition of the size a retention aid may beadded—typically Cartaretin PC. The mixture is then diluted to one literand the paper sheet is formed on a laboratory sheet former (basicallythis is a cylinder with a wire gauze at the bottom—the cylinder ispartly filled with water, the pulp suspension is added, air is thenblown through to ensure the pulp is well dispersed, a vacuum is thenapplied and the pulp slurry is pulled through the wire to leave a papersheet, this sheet is removed from the wire and pressed and dried). Thesheet is left in a humidity cabinet to achieve equilibrium and then thewhiteness is measured using a Datacolor ELREPHO 2000 spectrophotometer.The measured values show a surprisingly high whiteness degree and yield.

Application Example E

200 g of a pulp suspension (2.5% aqueous suspension of a 50% mixture ofbleached soft wood and hard wood pulps beaten to a freeness of about20°SR) is measured into a beaker and stirred and 20% filler suspension[40 g of 100 g/liter of a suspension of (M_(X8)) treated with theproduct of Example 1, in water] is added. After the addition the mixtureis stirred for a further 5 minutes and then 2% of rosin size solution isadded (typically—‘T size 22/30’ from Hercules), the mixture is stirredfor a further 2 minutes and then 3 ml of alum solution (50 g alum in 1liter water) are added and the mixture is stirred for a further 2minutes. The mixture is then diluted to one liter and the paper sheet isformed on a laboratory sheet former. The sheet is left in a humiditycabinet to achieve equilibrium and then the whiteness is measured usinga Datacolor ELREPHO 2000 Spectrophotometer. The measured values show asurprisingly high whiteness degree and yield.

Analogously as the product of Example 1, the products of each ofExamples 2 3 and 4 are employed in the above Application Examples C, Dand E.

1. A water soluble, amphoteric optical brightener compound of theaverage formulaX-[Z-Y]_(n) in which X is a precursor compound containing the structureof formula (Ib′)

wherein n is from 1 to 2, p is 0, 1 or 2, R₀′″ is hydrogen, methyl,methoxy or chlorine, M is hydrogen or an alkali metal cation, Z is atertiary amino group, covalently linking X to Y, and Y is the reactionproduct of epichlorohydrin with a polyfunctional aliphatic alcohol offormula (III′)H—(CHOH)_(x3)—H  (III′) with x3 being 3 to 6, and a primary, secondaryor tertiary mono- or polyamine or mixtures thereof.
 2. The opticalbrightener according to claim 1, wherein p is 1 or2, R₀′″ is hydrogen, Mis a Sodium cation, n and Z are defined as in claim 1 and Y is thereaction product of epichlorohydrin with D-sorbitol, glycerol ormixtures thereof and N,N-dimethylethanolamine, ethanolamine,triethylamine, isopropylamine, dimethylamine,N,N,N′,N′-tetramethylethylene diamine or mixtures thereof.
 3. A processfor the production of an amphoteric optical brightener compoundaccording to claim 1, wherein each mole of an optical brightenerprecursor of Formula (I)X-(Hal)_(m)  (I), wherein X is defined as in claim 1 Hal is halogen, andm is from 1 to 2, is condensed with n moles of an amine of Formula (II),HZ′-Y  (II), wherein Z′ is a secondary amino group, Y is defined as inclaim 1, and n is at least
 1. 4. The process according to claim 3,wherein Hal is chlorine, m is 2, and n is 2.